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This study examines the effects of different surface active soils on glassware deposition during mechanical dishwashing. Various variables such as detergent type, grease levels, and oatmeal and dry milk amounts were tested. The study found that liquid and powder detergents react differently to different soil types and amounts, and higher amounts of grease and oatmeal can reduce film and spots on glassware. The study also evaluates the precision of evaluation methods and discusses the importance of considering soil type and amount in detergent performance.
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SCIENTIFIC SERVICES S/D INC October 2004 ASTM D 3556 RESEARCH Deposition on Glassware During Mechanical Dishwashing Background 1 Preliminary Soil Exp. 3-5 3 Soils,2Levels, ½ Factorial 6-12 Precision of Evaluation 13-20 Preparation of Standards 20-24
PRELIMINARY EXPERIMENT - SENSITIVITY TO CURRENT D 3556 SOILS
Preliminary Test of Soil Effect - 2 Level Factorial Design – Main Effects OnlyLiquid and Powder commercial Detergents at recommended use levelEqual Amounts of Tallow/Lard/Margarine Greasy Soil – 16 or 48g Oatmeal+Dry Milk ASTM Soil - 16g or 48g165 ppm in Maytag MDB3700AWX
Conclusions from Preliminary Experiment • All three variables have significant effects. • Liquid and powder detergents react differently to soil kind and amount. Liquid Detergent gave more more spots than powder. Powder gave more film. • Higher amounts of grease reduced film but had no effect on spots. • Higher amounts of oatmeal reduced both film and spots. • Additional work was done with more realistic levels of soils and the three soils – fat, starch and protein were each investigated.
INVESTIGATION OF EFFECTS OF THREE “SURFACE ACTIVE” SOILS Variables Liquid and Powder Commercial Detergents at Recommended Dosage Hi and Low Levels of Grease Dry Milk Oatmeal Levels chosen to approximate household amounts Maytag Model No. MDB3700AWX inexpensive model 165 ppm 2/1 Ca/Mg synthetic hard water Evaluate after 1,2 3 Cycles by Rating and by Ranking
Experimental Design – Half Factorial – 4 Variables – 2 levels
Fractional Factorial Structure Factor Confounding Rules Dry Milk = Detergent X Grease X Oatmeal Aliasing Structure Detergent Grease Oatmeal Dry Milk Detergent X Grease = Oatmeal X Dry Milk Detergent X Oatmeal = Grease X Dry Milk Detergent X Dry Milk = Grease X Oatmeal
3rd Cycle Main Effects of 4 Variables from Experimental DesignEvaluation by Ranking and by Rating against Standards
1st, 2nd & 3rd Cycle Main Effects from 4 variable Experimental Design
Interactions from 4 Variable Design - Data from Evaluation by Ranking
Conclusions from study of three separate soils with Liquid and Powder DetergentsRanking results used. Ranking vs Rating Discussed Later • At the lower levels of soil significant effects were still seen and interactions between the variables were important. Also, there were differences after 1, 2, and 3 cycles. • Evaluation of 3rd cycle glasses only show more grease gave more spots. More oatmeal caused more film. More dry milk gave less film. With Liquid Detergent there were more spots and Powder resulted in more film • Including evaluations from all three cycles gives similar, but not identical, results. Grease causes both film and spots to increase. Oatmeal gives fewer spots. Dry Milk still gave less film. Powder detergent is preferred for less spotting but Liquid Detergent is better for less film. • There are many significant two way interactions between the variables. But, there is confounding because of the half-factorial experimental design, so don’t know whether the effects shown are soil-to-soil synergisms of their soil-detergent counterparts. The importance is that soil type and amount affect Detergent Performance differently and need to be taken into account.
Precision of Evaluation • Comparison of evaluation of sets of glasses by ranking best to worst versus rating against ASTM Standards. • Three Operators • Three separated Sessions • Analysis by JMP Statistical Software
Evaluation by Ranking and against Standards by 3 Observers 3 Times24 Miscellaneous FL Glasses
Evaluation of Glasses by 3 Observers 3 Times – 24 FL Glasses - Statistics
Effect of 3 Operators and 3 Sessions on Evaluation of 24 Glasses from Experimental Design
Statistics by Ranking and vs Stds. for 2 Level 4 Variable Partial Factorial Experimental Design
Interactions Data from 4 Variable Design by Evaluation Against Standards
Interactions – 3rd Cycle Results from 4 Variable Design Vs Standards and by Ranking
Conclusions about Rating vs Ranking • Operator differences cause less error when relative performance is evaluated by a procedure to rank an experimental set of glasses than when assignment of ratings against standard glasses is used. • Either procedure will allow for the measurement of significant differences in performance. And the operator error introduced by ranking is of low or significance. • Ranking is less stressful than Rating. • New data show that elapsed time before evaluation can be a factor and should be controlled.
Preparation of Spot and Film Standard Glasses • After much effort to select glasses from actual laboratory runs as spot and film standards, we developed methods for making spotted and filmed glasses “synthetically. Spots were made by spraying natural hard water. Film was made by applying a pigment dispersion. • To relate the ASTM 1- 5 scales to household usage we conducted a consumer “acceptance” test. Twenty four glasses with a wide range of deposits from various laboratory runs and including synthetically spotted and filmed glasses. The synthetic glasses had deposits that were typical of laboratory runs. Deposit amounts were related to concentration of applied so that the final scale would be linear with amount applied. • The consumer test was run in the panelists dishwasher. There were 12 panelists. The glasses were loaded into the dishwasher rack. The panelist was requested to remove the glasses and put them away or set them aside for rewashing. Acceptance or rejection was recorded. Data from the 10 synthetic filmy and spotty was plotted on Pareto Charts which follow. • From the charts we estimated the concentration at which all panelists would reject the glass as too spotty or filmy for use. This concentration was divided by four to give five levels of soil related to the ASTM Scale. • ASTM 1 No Deposit • ASTM 2 25% of Unacceptable Level • ASTM 3 50% of Unacceptable Level • ASTM 4 75 % of Unacceptable Level • ASTM 5 100% of Unacceptable Level • We are currently perfecting our techniques and measuring reproducibility. We plan to repeat the consumer study to confirm our initial results.
Future Work • Use the information about soil effects to conduct further performance evaluations • Refine the procedures to produce sets of standard spotted and filmed glasses to use as standards to rate dishwashing performance.
